The present invention relates to automatic fastening machines and methods, and, more specifically, to an apparatus and method for automatically assembling major subassemblies together.
Large objects, such as highway trailers and aircraft wings, typically comprise multiple major subassemblies fastened together. For example, a highway trailer includes major subassemblies such as a roof, side walls, and floor. The floor may include horizontal cross members connected to opposing side bottom rails. A floor deck is placed over the cross members and attached to the cross members. In the case of a sixty foot long highway trailer, the load demands and shear size of the major subassemblies require numerous points of attachment to ensure structural stability.
A wide variety of machines exist for attaching one major subassembly to another using bolts or rivets. These machines generally include a first unit to drill holes in the subassemblies, a supply of bolts or rivets, and a second unit to secure the bolts or upset the rivets in the subassemblies. Generally, the machines mount on a platform, and the platform moves relative to the subassemblies to position the machine at a desired attachment location.
To increase a trailer's structural integrity, it is preferable to attach the floor deck coincident with the cross beams. In the case of large subassemblies, however, the rivet or screw locations are often not uniformly spaced. For example, in the floor subassembly described above, adjacent cross members may be spaced at differing widths due to the presence of wheel axles, doorways and other design limitations. In addition, manufacturing tolerances result in slight variations in the distance between cross beams on each individual trailer and in the locations of cross beams on other trailers of the same general design and measurement.